[mythtv] transcoding with cutlist

Martin Moeller martin at martinm-76.dk
Tue Aug 12 00:38:52 EDT 2003

man, 2003-08-11 kl. 20:58 skrev Geoffrey Hausheer:
> Actually, I'm not totally sure about the last cutpoint but it
> > definately doesn't cut all it should from the end of the recording...
> This should all be fixed with my latest transcoding patches.
> > 
I'll take a look soon.

> > I guess the comments earlier on about mythtranscoder breaking mencoder
> > explains some of my problems but I also have problems with mplayer quite
> > often now. It seems to only happen on channels that have subtitle
> > information, though.
> I haven't worked with subtitles at all.  i have no idea how the
> transcoder will handle them.  If you have a nuv, I can look into making
> it work, but as for mplayer...that's not really my area of expertise.
I think they make the transition just fine <string/grep/less> yup, still
there after transcoding. It may or may not be what breaks mplayer. Most
likely it is some other change that possibly in combination with this
triggers the annoying behaviour I've seen.

> > 
> > I wonder how much work it would be to do either of the following:
> > 
> > 1) Add an option to skip text frames on reencoding. I'm not quite sure
> > if they are the problem or not and allegedly the 'patch to the patch'
> > that Ken fashioned ought to make it not a problem, but...
> I could do this, but I don't think it is a good idea.  It would just be a
> hack.  better to fix the mplayer patch, or mythtranscode if it is doing
> something wrong.
Yeah. I will take a closer look at new_demux_package, but I would hope
the original author of the patch rekindled his interest with the latest
CVS version of mythtv and found the problem. I have an indication or two
but not much clue as to the bigger picture...

> > 
> > 2) Transcode directly to DivX/Xvid .avi files (i.e. skipping all the
> > mythtv specific stuff. Basically what mencoder would do it it wasn't
> > broken.
> This is difficult.  It would involve really nasty things, and Isaac has
> said many times he's not interested in it.  It isn't impossible, but I
> won't work on it anymore.
All right.
> The option I was hoping for would be to use mythtranscode to decode raw
> frames, and then stream those directly to mencoder.  I haven't found a
> raw format (no header/sync frames) that mencoder will take as input, so
> haven't pursued this.  This would mean mencoder wouldn't need to know nuv
> format, so it'd be nice, but again, I'm not pursuing it any further.  If
> someone knows of a way to get mencoder to take streaming input, I'd be
> willing to do the mythtranscode part.
When you say streaming input I assume that standard input applies?
You can pipe data into mencoder like this:

cat somefile | mencoder -ovc lavc -oac mp3lame <other opts> -o output -

Or maybe this, if you can pass the MP3 audio along unaltered:

mythtranscoder <stdout> | mencoder -ovc lavc -oac copy <etc...> -

the '-' is the key here. As to what raw formats you can feed it and
whether you can give it both video and sound simultanously in raw mode
though, I'm not sure...

I don't expect you to look at this immediately or anything, but it you
have a couple of minutes to see if it works it would be really great.

These seems like the most relevant options, although the may be mplayer
options and not mencoder options:

       -rawaudio <option1:option2:...>
              This  option  lets  you  play  raw  audio files.  It may
also be used to play audio CDs which are not 44KHz 16Bit
              Available options are:

                      use raw audio demuxer
                      number of channels
                      rate in samples per second
                      sample size in byte
                      fourcc in hex

       -rawvideo <option1:option2:...>
              This option lets you play raw video files.
              Available options are:

                      use raw video demuxer
                      rate in frames per second, default 25.0
                      set standard image size
                      image width in pixels
                      image height in pixels
                      set colorspace
                      colorspace (fourcc) in hex
                      frame size in Bytes

> > 
> > I can put up a test .nuv file if you would like something to try out on
> > :)
> As I said, if there is a problem with mythtranscode (i.e. transcoded
> files won't play in myth), I'll be happy to look at it.
No problems inside myth, thankfully, only problems with too little free
harddisk space :-/

> .Geoff
Martin Moeller <martin at martinm-76.dk>

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